Level measurement plays a critical role in ensuring the safety and efficiency of the chemical process equipment utilized in the chemical industry, including liquid extraction, vapor/liquid separation, and mixing and blending. In this post, part of our series on chemical processing applications, Magnetrol® explores how level control instrumentation can improve the efficiency and safety of chemical process equipment. If you missed our first blog post, on level measurement solutions for the distilling process, you can read it here.

Liquid Extraction

Application: Liquid-liquid extraction (LLX), or solvent extraction or partitioning, is a selective separation procedure for isolating and concentrating a valuable substance from an aqueous solution by using an organic solvent. LLX can serve as an alternative when distillation is ineffective. LLX is used in pharmaceutical, food and agricultural processing, organic and inorganic chemistry, hydrometallurgy and fragrances.

Challenges: In mixer-settler type extraction, feed and solvent tanks are monitored for level. The feed and solvent are thoroughly blended in a mixer-settler chamber and the mixture overflows into a separation chamber where it settles into light and heavy phases. The separate phases are monitored and removed on interfacial level control.

Application: Where the separation of vapors and liquids is required, a separator drum, or knockout pot, flash drum, or compressor suction drum, is integrated into the process unit. The separation vessel receives the flashing liquid mixture where the liquid is subsequently gravity separated and falls to the bottom as the vapor exits at the top.

Challenges: Typically, a collection tank located beneath the separation chamber collects the liquid by gravity flow and utilizes a liquid level control for liquid withdrawal. The control also maintains a vapor barrier while discharging the collected liquid at the same rate of accumulation. In some separators, such as flash drums, liquid level must be kept within an extremely narrow span for very tight control.

Application: Scrubbers remove odors, pollutants, acid gases and chemical wastes from air and liquid streams. In a wet scrubber, the polluted stream flows counter currently past water or a liquid chemical which removes the undesirable component of the gas or liquid. Chemical scrubbing typically requires large amounts of caustic chemicals.

Challenges: Accurate level monitoring of the scrubbing water necessitates a control to automatically feed the correct amount of make-up water to the recycle reservoir either continuously or on a periodic basis. Located in the wet scrubber shell, the level monitoring device for water-out control should be equipped with a level alarm.

Application: Mixing and blending of liquid ingredients is essential throughout the broader chemical industry. In-line and skid mounted systems include batch and continuous mixing for liquid/liquid formulation and blending. An impeller in the process vessel accomplishes the mixing of miscible liquids.

Challenges: A mixing and blending system can be as simple as a vessel with an agitator and graduate in complexity to a fully skid-mounted PLC controlled system with heating, cooling, homogenization and steam injection capabilities. Level controls monitor tank and vessel levels and trigger alarms in underfill and overfill incidents.

Be sure to follow our blog in the coming weeks as we discuss level control for other chemical process equipment, including fermentation vessels, steam and surge drums, catalysis vessels, and the chlor-alkali process.

It’s interesting that you mentioned scrubbers removing pollutants from a liquid. My brother and I have been looking for something to separate the chemicals we’ve been working with. I’ll keep this in mind before choosing equipment.

Separation of chemical equipment can be done on various level and there are different techniques to do that which you have mentioned well. Yes, I do agree that control instrumentation can surely improve the efficiency and safety of chemical process equipment which will help a lot. Thanks.Chemical solvents